Which of the following is NOT a measure of schedule efficiency?

The Cost Performance Index (CPI) is primarily a measure of cost efficiency rather than schedule efficiency. It evaluates the cost efficiency of a project by comparing the budgeted cost of work performed to the actual costs incurred.

In contrast, Earned Value Analysis, Schedule Performance Index (SPI), and Budgeted Cost of Work Performed are all specifically concerned with the progress and timing aspects of a project's schedule. Earned Value Analysis provides an integrated perspective that combines both scope and schedule. The Schedule Performance Index is a specific metric used to assess how well the project is adhering to its scheduled timeline, relative to the planned schedule. Budgeted Cost of Work Performed relates to the budgeted amount for work accomplished over a specific period and is also connected to scheduling since it reflects time-equivalent work completed.

Thus, while CPI is an essential metric in project management, it does not measure schedule efficiency, making it the correct answer to the question of which option does not belong in the context of assessing schedule performance.